Medical stapling devices exist in the art. Ethicon Endo-Surgery, Inc. (a Johnson & Johnson company; hereinafter “Ethicon”) manufactures and sells such stapling devices. Circular stapling devices manufactured by Ethicon are referred to under the trade names PROXIMATE® PPH, CDH and ILS and linear staplers are manufactured by Ethicon under the trade names CONTOUR and PROXIMATE. In each of these exemplary surgical staplers, tissue is compressed between a staple cartridge and an anvil and, when the staples are ejected, the compressed tissue is also cut. Depending upon the particular tissue engaged by the physician, the tissue can be compressed too little (where blood color is still visibly present in the tissue), too much (where tissue is crushed), or correctly (where the liquid is removed from the tissue, referred to as dessicating or blanching.)
Staples to be delivered have a given length and the cartridge and anvil need to be within an acceptable staple firing distance so that the staples close properly upon firing. Therefore, these staplers have devices indicating the relative distance between the two planes and whether or not this distance is within the staple length firing range. Such an indicator is mechanical and takes the form of a sliding bar behind a window having indicated thereon a safe staple-firing range. These staplers are all hand-powered, in other words, they require physical actuations by the user/physician to position the anvil and stapler cartridge about the tissue to be stapled and/or cut, to close the anvil and stapler cartridge with respect to one another, and to fire and secure the staples at the tissue (and/or cut the tissue). No prior art staplers are electrically powered to carry out each of these operations because the longitudinal force necessary to effect staple firing is typically on the order of 250 pounds at the staple cartridge. Further, such staplers do not have any kind of active compression indicator that would optimizes the force acting upon the tissue that is to be stapled so that tissue degradation does not occur.
One hand-powered, intraluminal anastomotic circular stapler is depicted, for example, in U.S. Pat. No. 5,104,025 to Main et al., and assigned to Ethicon. Main et al. is hereby incorporated herein by reference in its entirety. As can be seen most clearly in the exploded view of FIG. 7 in Main et al., a trocar shaft 22 has a distal indentation 21, some recesses 28 for aligning the trocar shaft 22 to serrations 29 in the anvil and, thereby, align the staples with the anvils 34. A trocar tip 26 is capable of puncturing through tissue when pressure is applied thereto. FIGS. 3 to 6 in Main et al. show how the circular stapler 10 functions to join two pieces of tissue together. As the anvil 30 is moved closer to the head 20, interposed tissue is compressed therebetween, as particularly shown in FIGS. 5 and 6. If this tissue is overcompressed, the surgical stapling procedure might not succeed. Thus, it is desirable to not exceed the maximum acceptable tissue compression force. The interposed tissue can be subject to a range of acceptable compressing force during surgery. This range is known and referred to as optimal tissue compression or OTC, and is dependent upon the type of tissue being stapled. While the stapler shown in Main et al. does have a bar indicator that displays to the user a safe staple-firing distance between the anvil and the staple cartridge, it cannot indicate to the user any level of compressive force being imparted upon the tissue prior to stapling. It would be desirable to provide such an indication so that over-compression of the tissue can be avoided.